Photoconductive substances for use in a photoconductive layer of an electrophotographic light-sensitive material that have heretofore been known include inorganic compounds such as amorphous selenium, selenium alloys, and metal compound semiconductors (e.g., oxides, sulfides, and selenides of metals such as cadmium and zinc), organic polymers such as polyvinyl carbazole, organic compounds such as dyes and pigments, and the like. In recent years it has been proposed to use photoconductive amorphous silicon in the formation of a photoconductive layer for electrophotographic light-sensitive materials.
These electrophotographic light-sensitive materials utilizing amorphous silicon as a photoconductive substance basically comprise an electrically conductive support and a photoconductive layer provided on the support, said layer being made of amorphous silicon, which may also contain hydrogen and/or halogen atoms. The photoconductive layer of amorphous silicon is formed by techniques such as a method in which powdered amorphous silicon is dispersed in a binder and then applied onto an electrically conductive support, and a method in which a silicon-containing gas, such as silane and silane derivatives, is decomposed by glow discharge and deposited on an electrically conductive support.
However, electrophotographic light-sensitive materials consisting of an electrically conductive support and an amorphous silicon photoconductive layer alone exhibit various problems in the practical use thereof.
One of the problems is that upon application of corona discharge, particularly negative corona discharge under conditions of high temperature and high humidity (for example, during midsummer), a serious reduction in resolving power occurs. This reduction in resolving power occurs even if the formation of an oxidized layer of amorphous silicon is prevented by providing an overcoat layer on the amorphous silicon as disclosed in Japanese Patent Application (OPI) No. 115551/82 (the term "OPI" as used herein means a "published unexamined Japanese patent application"), and Japanese Patent Application No. 57975/83. Thus, this reduction in resolving power is entirely different from that due to the formation of an oxidized layer of amorphous silicon.
Such a reduction in resolving power and subsequent formation of dull images under high temperature/humidity conditions are very detrimental in electrophotography. It has therefore been desired to overcome the foregoing problems.